diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 8e11052..ea3c82c 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -7,6 +7,7 @@ on:
 jobs:
   build:
     strategy:
+      fail-fast: false
       matrix:
         python-version: ["3.9", "3.10", "3.11"]
         os: [ubuntu-latest, windows-latest, macos-latest]
diff --git a/bpx/__init__.py b/bpx/__init__.py
index 6c62ecf..c7e2ca2 100644
--- a/bpx/__init__.py
+++ b/bpx/__init__.py
@@ -5,7 +5,7 @@
 from .schema import BPX, check_sto_limits
 from .utilities import get_electrode_concentrations, get_electrode_stoichiometries
 
-__version__ = "0.4.2"
+__version__ = "0.5.0"
 
 __all__ = [
     "BPX",
diff --git a/bpx/function.py b/bpx/function.py
index 51e2d71..fff4155 100644
--- a/bpx/function.py
+++ b/bpx/function.py
@@ -3,7 +3,6 @@
 import copy
 import tempfile
 from importlib import util
-from pathlib import Path
 from typing import TYPE_CHECKING, Any
 
 from pydantic_core import CoreSchema, core_schema
@@ -87,26 +86,10 @@ def to_python_function(self, preamble: str | None = None) -> Callable:
         source_code = preamble + function_def + function_body
 
         with tempfile.NamedTemporaryFile(suffix=f"{function_name}.py", delete=False) as tmp:
-            # write to a tempory file so we can
-            # get the source later on using inspect.getsource
-            # (as long as the file still exists)
-            tmp.write((source_code).encode())
+            tmp.write(source_code.encode())
             tmp.flush()
-
-            # Now load that file as a module
             spec = util.spec_from_file_location("tmp", tmp.name)
             module = util.module_from_spec(spec)
             spec.loader.exec_module(module)
 
-            # Delete
-            tmp.close()
-            Path(tmp.name).unlink(missing_ok=True)
-            if module.__cached__:
-                cached_file = Path(module.__cached__)
-                cached_path = cached_file.parent
-                cached_file.unlink(missing_ok=True)
-                if not any(cached_path.iterdir()):
-                    cached_path.rmdir()
-
-        # return the new function object
         return getattr(module, function_name)
diff --git a/bpx/parsers.py b/bpx/parsers.py
index e6405b4..a361646 100644
--- a/bpx/parsers.py
+++ b/bpx/parsers.py
@@ -1,3 +1,8 @@
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
 from .schema import BPX
 
 
@@ -26,13 +31,13 @@ def parse_bpx_obj(bpx: dict, v_tol: float = 0.001) -> BPX:
     return BPX.model_validate(bpx)
 
 
-def parse_bpx_file(filename: str, v_tol: float = 0.001) -> BPX:
+def parse_bpx_file(filename: str | Path, v_tol: float = 0.001) -> BPX:
     """
     A convenience function to parse a bpx file into a BPX model.
 
     Parameters
     ----------
-    filename: str
+    filename: str or Path
         a filepath to a bpx file
     v_tol: float
         absolute tolerance in [V] to validate the voltage limits, 1 mV by default
@@ -42,18 +47,12 @@ def parse_bpx_file(filename: str, v_tol: float = 0.001) -> BPX:
     BPX: :class:`bpx.BPX`
         a parsed BPX model
     """
-
-    from pathlib import Path
-
-    bpx = ""
-    if filename.endswith((".yml", ".yaml")):
+    if str(filename).endswith((".yml", ".yaml")):
         import yaml
 
         with Path(filename).open(encoding="utf-8") as f:
             bpx = yaml.safe_load(f)
     else:
-        import orjson as json
-
         with Path(filename).open(encoding="utf-8") as f:
             bpx = json.loads(f.read())
 
@@ -77,7 +76,5 @@ def parse_bpx_str(bpx: str, v_tol: float = 0.001) -> BPX:
     BPX:
         a parsed BPX model
     """
-    import orjson as json
-
     bpx = json.loads(bpx)
     return parse_bpx_obj(bpx, v_tol)
diff --git a/pyproject.toml b/pyproject.toml
index 16e300a..57fd24f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -32,7 +32,6 @@ dependencies = [
     "pydantic >= 2.6",
     "pyparsing",
     "pyyaml",
-    "orjson",
 ]
 
 [project.urls]
diff --git a/tests/test_schema.py b/tests/test_schema.py
index 99be0a6..133e6c4 100644
--- a/tests/test_schema.py
+++ b/tests/test_schema.py
@@ -1,6 +1,7 @@
 import copy
 import unittest
 import warnings
+from typing import Any
 
 import pytest
 from pydantic import TypeAdapter, ValidationError
@@ -12,7 +13,7 @@
 
 class TestSchema(unittest.TestCase):
     def setUp(self) -> None:
-        self.base = {
+        self.base : dict[str, Any] = {
             "Header": {
                 "BPX": 1.0,
                 "Model": "DFN",
@@ -200,26 +201,26 @@ def setUp(self) -> None:
         }
 
     def test_simple(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         adapter.validate_python(test)
 
     def test_simple_spme(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Header"]["Model"] = "SPMe"
         adapter.validate_python(test)
 
     def test_simple_spm(self) -> None:
-        test = copy.copy(self.base_spm)
+        test = copy.deepcopy(self.base_spm)
         adapter.validate_python(test)
 
     def test_bad_model(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Header"]["Model"] = "Wrong model type"
         with pytest.raises(ValidationError):
             adapter.validate_python(test)
 
     def test_bad_dfn(self) -> None:
-        test = copy.copy(self.base_spm)
+        test = copy.deepcopy(self.base_spm)
         test["Header"]["Model"] = "DFN"
         with pytest.warns(
             UserWarning,
@@ -228,7 +229,7 @@ def test_bad_dfn(self) -> None:
             adapter.validate_python(test)
 
     def test_bad_spme(self) -> None:
-        test = copy.copy(self.base_spm)
+        test = copy.deepcopy(self.base_spm)
         test["Header"]["Model"] = "SPMe"
         with pytest.warns(
             UserWarning,
@@ -237,7 +238,7 @@ def test_bad_spme(self) -> None:
             adapter.validate_python(test)
 
     def test_bad_spm(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Header"]["Model"] = "SPM"
         with pytest.warns(
             UserWarning,
@@ -246,7 +247,7 @@ def test_bad_spm(self) -> None:
             adapter.validate_python(test)
 
     def test_table(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Parameterisation"]["Electrolyte"]["Conductivity [S.m-1]"] = {
             "x": [1.0, 2.0],
             "y": [2.3, 4.5],
@@ -254,7 +255,7 @@ def test_table(self) -> None:
         adapter.validate_python(test)
 
     def test_bad_table(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Parameterisation"]["Electrolyte"]["Conductivity [S.m-1]"] = {
             "x": [1.0, 2.0],
             "y": [2.3],
@@ -266,23 +267,23 @@ def test_bad_table(self) -> None:
             adapter.validate_python(test)
 
     def test_function(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Parameterisation"]["Electrolyte"]["Conductivity [S.m-1]"] = "1.0 * x + 3"
         adapter.validate_python(test)
 
     def test_function_with_exp(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Parameterisation"]["Electrolyte"]["Conductivity [S.m-1]"] = "1.0 * exp(x) + 3"
         adapter.validate_python(test)
 
     def test_bad_function(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Parameterisation"]["Electrolyte"]["Conductivity [S.m-1]"] = "this is not a function"
         with pytest.raises(ValidationError):
             adapter.validate_python(test)
 
     def test_to_python_function(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Parameterisation"]["Electrolyte"]["Conductivity [S.m-1]"] = "2.0 * x"
         obj = adapter.validate_python(test)
         funct = obj.parameterisation.electrolyte.conductivity
@@ -290,13 +291,13 @@ def test_to_python_function(self) -> None:
         assert pyfunct(2.0) == 4.0
 
     def test_bad_input(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Parameterisation"]["Electrolyte"]["bad"] = "this shouldn't be here"
         with pytest.raises(ValidationError):
             adapter.validate_python(test)
 
     def test_validation_data(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Validation"] = {
             "Experiment 1": {
                 "Time [s]": [0, 1000, 2000],
@@ -314,39 +315,39 @@ def test_validation_data(self) -> None:
 
     def test_check_sto_limits_validator(self) -> None:
         warnings.filterwarnings("error")  # Treat warnings as errors
-        test = copy.copy(self.base_non_blended)
+        test = copy.deepcopy(self.base_non_blended)
         test["Parameterisation"]["Cell"]["Upper voltage cut-off [V]"] = 4.3
         test["Parameterisation"]["Cell"]["Lower voltage cut-off [V]"] = 2.5
         adapter.validate_python(test)
 
     def test_check_sto_limits_validator_high_voltage(self) -> None:
-        test = copy.copy(self.base_non_blended)
+        test = copy.deepcopy(self.base_non_blended)
         test["Parameterisation"]["Cell"]["Upper voltage cut-off [V]"] = 4.0
         with pytest.warns(UserWarning):
             adapter.validate_python(test)
 
     def test_check_sto_limits_validator_high_voltage_tolerance(self) -> None:
         warnings.filterwarnings("error")  # Treat warnings as errors
-        test = copy.copy(self.base_non_blended)
+        test = copy.deepcopy(self.base_non_blended)
         test["Parameterisation"]["Cell"]["Upper voltage cut-off [V]"] = 4.0
         BPX.Settings.tolerances["Voltage [V]"] = 0.25
         adapter.validate_python(test)
 
     def test_check_sto_limits_validator_low_voltage(self) -> None:
-        test = copy.copy(self.base_non_blended)
+        test = copy.deepcopy(self.base_non_blended)
         test["Parameterisation"]["Cell"]["Lower voltage cut-off [V]"] = 3.0
         with pytest.warns(UserWarning):
             adapter.validate_python(test)
 
     def test_check_sto_limits_validator_low_voltage_tolerance(self) -> None:
         warnings.filterwarnings("error")  # Treat warnings as errors
-        test = copy.copy(self.base_non_blended)
+        test = copy.deepcopy(self.base_non_blended)
         test["Parameterisation"]["Cell"]["Lower voltage cut-off [V]"] = 3.0
         BPX.Settings.tolerances["Voltage [V]"] = 0.35
         adapter.validate_python(test)
 
     def test_user_defined(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Parameterisation"]["User-defined"] = {
             "a": 1.0,
             "b": 2.0,
@@ -358,7 +359,7 @@ def test_user_defined(self) -> None:
         assert obj.parameterisation.user_defined.c == 3
 
     def test_user_defined_table(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Parameterisation"]["User-defined"] = {
             "a": {
                 "x": [1.0, 2.0],
@@ -368,12 +369,12 @@ def test_user_defined_table(self) -> None:
         adapter.validate_python(test)
 
     def test_user_defined_function(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         test["Parameterisation"]["User-defined"] = {"a": "2.0 * x"}
         adapter.validate_python(test)
 
     def test_bad_user_defined(self) -> None:
-        test = copy.copy(self.base)
+        test = copy.deepcopy(self.base)
         # bool not allowed type
         test["Parameterisation"]["User-defined"] = {
             "bad": True,